Why must iPhone backups hoard space on my C drive?

I have a 500 GB “C” drive on my Windows 10 PC. Guess how much of that is used for iPhone backup data? Close to 200 GB or about 42% of the drive. That is just for me and my wife. I guess I can’t back up my kids phones. Even worse, I’m just about out of space on that drive at this point. Whatever shall we do?

As far as I know, Apple provides no supported way to change the drive where that data is stored (but please correct me if I’m wrong). Luckily, we can use a low level Windows feature to trick iTunes. We’ll create a secret “link” (technically called a “junction”) from where iTunes wants to store the backups to a different location. By default for me, the backups are stored here:

%APPDATA%\Apple Computer\MobileSync\Backup

which for me is:

C:\Users\[username]\AppData\Roaming\Apple Computer\MobileSync\Backup

So, we first move that Backup folder where we wish it was, such as a secondary hard drive. Luckily, I have just such a hard drive on my system. It has the drive letter “D.” So, I took that Backup folder and put it here: “D:\Apple\MobileSync\Backup” Your system may vary so you’ll need to modify the line below to make it work. I also made a copy of the Backup folder elsewhere just to be safe until everything was working.

Finally, run this (after suitably modifying to fit your system) from the command prompt:

Now, when iTunes tries to save data to the “Backup” folder it will transparently, without it even knowing, save that data in your desired folder, “D:\Apple\MobileSync\Backup” in my case. Even as you browse the system, the original folder will appear to be there, but you’ll see the files actually appear on the second drive as well. You’ll notice a little “shortcut” arrow on the folder icon to indicate it is a junction.

Try this at your own risk – things could have changed since this was written and it is possible doing things like this can mess up your system. It could also potentially make your backups not work cause who knows what changes might come to iTunes, although in theory iTunes knows nothing about the change we made. Anyway, you’ve been warned so do your own research and proceed with caution.